1. Field of the Invention
The invention relates to flat panel display (FPD) technology, and in particular to a self-emission type FPDs, in which a material layer used for fabrication of the active layers or the gate electrode layers in thin film transistors is employed as an electrical connection to the power lines that are used for the light-emitting devices.
2. Description of the Related Art
The demand for flat panel displays (FPDs), such as self-emission type FDPs, has increased rapidly in recent years. Self-emission type FDPs, such as active matrix organic light-emitting device (AMOLED) displays, typically employ an organic light-emitting diode (OLED) as a light-emitting device in a pixel region for displaying images. In a sub-pixel array of an AMOLED display, each sub-pixel unit typically includes a sub-pixel unit circuit constituted by a data line DL, a scan line SL, a power line PL, a switching thin film transistor (TFT) SW, a driving TFT DR, a storage capacitor C, and a light-emitting diode D′, as shown in FIG. 1.
In AMOLED products, the power line width is designed as wide as possible in order to reduce the voltage drop when a large current passes therethrough. Moreover, in order to improve the voltage uniformity at the source terminal of each driving TFT, the power lines are usually designed and fabricated to form a meshed structure, such that the power lines corresponding to the sub-pixels in each row of the pixel array can be electrically connected to each other. Since the power lines have a meshed structure and the data lines are fabricated by the same metal layer, portions of the meshed structure formed by power lines must extend across the data lines. Accordingly, in the circuit design, the intersections between the data lines and the portions of the meshed structure formed by power lines extended across the data lines must have additional interconnection bridges (which includes at least two via holes), and thus increases layout and fabrication complexity. Moreover, since each pixel size is limited by the area used for fabricating the meshed structure, further increasing display resolution (pixel per inch, ppi) is limited.
Therefore, a need exists in the art for development of an improved power line structure for OLED displays, capable of improving voltage uniformity while increasing display resolution.